The present invention relates to a projection type color display device which separates light of a light source into three color light fluxes at a spectrum optical system for split into color light fluxes of red, green and blue and guides respective color light fluxes thus separated to enter more than one image display element with a matrix layout of pixels having light intensity modulation means and then causes an enlarged projector device to project in an enlarged form the light with its light intensity modulated by the image display element in response to an image signal. More particularly, but not exclusively, this invention relates to a projection type color display device which is excellent in light use efficiency even in cases where a red light flux energy-reduced ultra-high pressure mercury lamp, a xenon lamp, a metal halide lamp or the like is used as the light source. The invention also relates to a rear-projection type color display apparatus which uses the projection type color display device to project a projection image therefrom by way of an optical fold mirror in an enlarged form onto a translucent screen that is provided at a prespecified location of a cabinet.
In recent years, projection type color display devices have been actively developed, which have a polarized light conversion device for converting light from a white light source into the same polarized wave, a light flux spectrum optical system made up of a dichroic mirror for split into respective color rays of red (R), green (G) and blue (B), optical path turn-back or fold mirrors for folding the optical paths of the red, green and blue light fluxes respectively, image display elements provided in a way corresponding to respective color light fluxes and having a matrix array of picture elements or “pixels” with the means for modulating the light intensity of each luminous flux correspondingly to an image signal to thereby form an optical image, a photosynthetic optical system which is formed by adhesion of prisms with provision of an optical filter for superposing optical images thus formed by these image display elements respectively to thereby provide a color image, and a projection optical system for projecting the color image superposed by this synthetic optical system in an enlarged form onto a viewing screen.
In these projection type color display devices, there is used the one with combination of one set of “fly eye” lenses, called an integrator optical system, in its illumination system for the purposes of achieving higher luminance and making on-screen luminance uniform.
Furthermore, the light source is designed to use a metal halide lamp of the short arc type having a light-emitting tube with a metal halogenide sealed therein for utilizing light emission unique to such metal to shorten the distance between electrodes, an ultra-high pressure mercury lamp which is easy to attain higher luminance, a xenon lamp with enhanced vivid coloring performance or “colorability,” and other similar suitable lamps. Among them, the ultrahigh pressure mercury lamp is high in luminance and short in arc length while offering the functionality resembling that of a point source so that the light use efficiency is excellent when combining it with the integrator optical system and also excellent in uniformity of on-screen luminance.
One example of the above-noted projection type color display devices is the one using transmissive liquid crystal panels as the image display elements thereof, a configuration of which is disclosed, for example, in JP-A-2003-5167.